The movie opens with Dr. John Watson (Jude Law) and Inspector Lestrade (Eddie Marsan) riding in a carriage in the middle of the night. The scene cuts from the carriage to Sherlock Holmes (Robert Downey Jr.) who is following on foot. He’s in a tremendous hurry – he darts between columns, up and down stairs and around buildings effortlessly – and finally enters a non-descript building.

Once inside, Holmes starts running down a spiral staircase, but pauses when he notices a ruffian who is standing guard. He analyzes the situation (the audience actually sees in slow-motion how Holmes plans to take the ruffian guard out), and then disarms the ruffian. Holmes continues running down the stairs, until he reaches the basement, where a black magic ritual is taking place. Holmes hides behind a column to assess the situation again.

In the center of the room, there’s a girl wearing a white dress and lying on a table, while a hooded figure stands over her chanting. Scattered across the room are several other hooded figures and ruffian guards. Holmes begins calculating how to take them out, but is interrupted when a guard comes up from behind him. He fights with the guard, then Watson shows up and helps Holmes choke the man. They greet each other with amusing banter (their friendship is very much written as a bromance, and come up at several points in the film), where Watson chides Holmes for forgetting to bring his pistol AND forgetting to turn off the stove.

Once the fighting really begins, most of the other hooded figures scatter. The main figure standing independent over the girl stays however, and his chanting begins to reach a feverish pitch. Holmes continues to fight and is helped by Watson.

Back at the table, the (possibly possessed) girl reaches up for a dagger and makes to stab herself. Holmes hurries over and stops her just in time. The hooded figure stops to greet Sherlock by name, and is revealed to be Lord Blackwood (Mark Strong). As he taunts Sherlock, Watson comes running over, but is stopped by Holmes. Turns out, Lord Blackwood had some kind of glass knife that would have pierced Watson if he had gotten any closer. Holmes directs Watson to put his energies into tending the girl, and Lestrade and his men burst in just in the nick of time.

As Blackwood is led off by Scotland Yard, Lestrade chides Holmes for not waiting for Lestrade’s orders. Holmes says that the girls parents hired him, so he doesn’t report to Lestrade. Before Lestrade can retort, a newspaper photographer who wants to take their picture interrupts him. Holmes throws up an arm and prevents the camera from capturing his face. Thus, all the credit is given to Lestrade instead.

The credits flash by and consist of newspaper headlines detailing Holmes and Watson’s exploits.

The scene now cuts to Baker Street, where Watson is treating an elderly patient.

As he dresses, the patient asks about Watson’s plans to move his medical practice to a new headquarters. Watson confirms that he is moving, and that he hopes to have the touch of a woman around the place soon. The patient congratulates him on his (potential – as Watson hasn’t proposed yet) nuptials, before nervously asking if Holmes is moving too. Watson says no, but is promptly interrupted by several loud blasts that send both men ducking for cover.

The patient leaps up and says that the blasts must be gunfire, but Watson soothes him and tells him that Holmes is probably hanging a picture with nails and hammer. Watson ducks out to check on the commotion, and is met by their housekeeper Mrs. Hudson (Geraldine James). She tells Watson that Holmes is in a mood, and she hopes that he can calm Sherlock down. At this point, the elderly patient comes out and is about to talk, when there’s the sound of gunfire again. Watson tells Mrs. Hudson to get the patient a cup of tea, and he’ll go see to Holmes himself. He also asks Mrs. Hudson to bring some food to cheer Sherlock up.

When Watson walks into Holmes’s study, the entire room is dark.

Watson comments into the darkness that he knows Holmes bored, as it’s been awhile since he’s had a case. Holmes remarks that he’s trying to figure out a way to silence the sound of gunfire, and Watson sarcastically retorts that it’s clearly not working. As Watson talks, he goes around opening up the blinds in the room, which causes Holmes to groan painfully.

Watson starts rifling through Holmes’s mail and offers him prospective cases to consider. Holmes flippantly independent solves all of them without a second thought. Watson also points out that Holmes is in the papers again, as Lord Blackwood is about to be hanged. We also learn that Watson will be the attending physician at the hanging, as he considers it a good away to conclude his final adventure with Holmes.

Mrs. Hudson comes in with tea and snacks, points out that the family bulldog is lying immobile on the floor, saying that Holmes has killed the dog, again. Watson hurried over to check on the animal, and asks Sherlock what he’s done to the dog now. Holmes nonchalantly says he was just testing out a new anesthetic.

Nothing seems to be cheering Holmes up, so Watson throws down the mail and tells Holmes that he needs to get out of the house. He tells Holmes that he’s going to join Watson and his future fiancée for dinner at a London hotel. Holmes begrudgingly agrees.

We cut to the hotel and pan through a crowd of elegantly dining men and women.

Holmes is sitting alone at a table, well dressed but looking incredibly uncomfortable. He checks his watch several times before Watson and Mary Morstan (Kelly Reilly) shows up. They chitchat, and Holmes’ deductive powers come up. Mary shows some suspicion at Holmes’ deduction skills. He points out several details about Watson simply from his walking stick, indicating that he is a decorated army veteran of the Afghan Wars. Mary asks Sherlock to analyze her, over Watson’s objections. He points out that she’s a governess and has been engaged once before, but likely broke off the engagement because the fiancé wasn’t wealthy enough for her. By this point Mary is starting to be come increasingly uncomfortable with Holmes’ comments, but Holmes doesn’t notice her discomfort or Watson’s warnings. He just continues rambling on. He also adds that she’s probably trying to do better this time around – e.g. finding a doctor to wed. Mary’s extremely offended by his comment, and tosses a glass of wine in his face. She then tells him that everything he said was true, but her first fiancé died. She then gets up to leave, throughly upset by Holmes’ rudeness, and is followed by Watson. Holmes remains at the table and has his dinner, alone.

Cut to Holmes fighting a much larger man in a boxing ring. He’s getting pummeled by the larger man and seems to be losing. He’s suddenly distracted by the appearance of a white handkerchief at the side of the ring with the initials “IA.” He scans the room and sees Irene Adler (Rachel McAdams), who then winks at him. Holmes makes to leave the rink – to the great disappointment of those cheering him on – but stops when his opponent spits on him.

Using the deductive logic we saw earlier, Holmes figures out how to use the handkerchief and some well-calculated moves to take out opponent. He carries them out with blinding speed to the shock and surprise of everyone in the room. When the opponent hits the ground, the entire room falls silent in shock, and someone actually says, “Where did THAT come from?” Holmes looks around, and realizes that Irene’s gone. He takes the money from a bookie and leaves.

Over at Scotland Yard, the prison guards are trying to deal with a potential riot. Lord Blackwood has caused a guard to come down with seizures, and no one wants to be around him for fear of his black magic. One of the braver guards asks him what he wants, and he says that he wants to talk to Holmes. It’s his final request.

Cut to Watson walking up the stairs in a rundown building. He goes into a room, where we see Holmes under the influence of cocaine, strumming away at a violin. Holmes greets Watson, and gestures to a bottle with flies.

He tells Watson that when he plays a certain pitch, the flies will fly in a counterclockwise direction. Watson sighs and asks him how long it took Holmes to catch the flies, and Holmes admits about six hours or so. Watson raises his eyebrows and goes “Really? What if I do this…?” and opens up the lid, letting all of the flies escape. Watson then tells Holmes to get up and get decent, as Blackwood has requested to see him.

Watson brings Holmes to the prison. On the carriage ride over, Holmes attempts to engage Watson in conversation, but Watson rebuffs him. Finally, Watson punches Holmes in the nose and tells Sherlock that he had already known about Mary’s previous fiancé. They bicker for a while, and finally arrive at the prison.

Most of the guards are afraid of getting too close to Lord Blackwood, so Holmes tells them that he can find his way out own his own. Blackwood greets him, and tells Sherlock that Blackwood isn’t done killing just yet. He’s planning on killing three more people, and there’s nothing Holmes can do about it. He also tells Holmes that trying to stop him will be an extremely futile gesture. Holmes ignores him, and makes several remarks about Blackwood’s upcoming hanging and makes offhand comments about how even though Blackwood was cunning, his devious plans were going to come into an end. Finally Holmes leaves without paying much thought to Blackwood’s warnings.

Cut to a British court where Lord Blackwood is sentenced and hanged. After the hanging, Watson feels for a pulse, and then legally declares him dead.

Cut to Holmes sleeping in his study. We see a woman’s gloved hand cracking walnuts, which wake Holmes up. We discover that Irene Adler is in the study with Holmes, and she’s brought him food from her travels. It is obvious the two has met before. Holmes looks rather unnerved and begins hastily straightening up the place; including slamming a portrait of Irene that he has on his desk facedown.

The two of them banter for a bit, and there’s obviously some kind of romantic chemistry there. Holmes wryly comments on her con artist talents, and Irene just shrugs it off. She tells him that she needs him for a case, and hands him an envelope with information and money. She then gets up to leave, but not before putting Holmes’ portrait of her into an upright position again. Sherlock strums at his violin and watches her leave.

Irene runs into Watson at the door, and greets him. Watson seems rather stunned, but doesn’t say anything. We follow Irene down the street, until she gets into a carriage with a figure sitting in the shadows. She tells him that she’s sure Holmes will agree to take the case. Their conversation is interrupted by a street bum who lurches up to the car, but is quickly scared off by the shadow-y man’s wrist pistol.

Cut back to Baker Street, where Watson chastises Holmes for falling for Irene. Holmes denies this, but Watson continues to tease him about this. Watson reveals that the case Irene wants Holmes to solve involves him finding a ginger dwarf. He makes some jokes about Irene’s taste in men, and asks Holmes what he was doing. Holmes starts to explain, and the story flashes back to what Holmes was doing while Irene was walking down to the carriage. Watson is going up the stairs when he sees Holmes trying to open a window. He tries to ask Holmes what he is doing, but Holmes is obviously in a hurry, and he doesn’t explain anything to Watson. Holmes jumps out the window and crashes. Watson sighs and closes the window, ignoring Holmes. Holmes runs down the allyways, following Irene. Along the way, he picks up some disguises, and finally reveals that the street bum was actually he. He also comments about the man in the carriage, claming that Irene is scared of him. Watson is surprised by this, saying that Irene isn’t scared of anyone.

As they’re talking, a constable from Scotland Yard comes in and tells them that Lord Blackwood has apparently risen from the grave. Holmes wants Watson to come with him, but Watson says he needs to visit with Mary. Holmes obviously wants Watson to come with him, so he berates Watson for not caring about his reputation, saying that no girl wants to marry a man who can’t tell if a man is dead or not. Watson finally agrees to go. They’re taken to the cemetery to meet with Lestrade, where the limestone outside of Blackwood’s mausoleum has shattered. Holmes examines the scene and licks a piece of the stone and waits as Lestrade and his men bring the coffin out. Once they open the coffin, the body inside turns out to be that of Irene’s red-haired man.

Holmes examines the body, and declares the man probably died about twelve hours ago. He also takes the man’s watch without anyone noticing, and then tells Lestrade he’ll follow up. Holmes and Watson leave the cemetery.

Cut to Watson and Holmes walking down a London street, where Holmes discusses the initials scratched on the watch. Holmes tests Watson’s deducing skills by having him explain the marks. Watson deduces that they’re the markings of pawnbrokers, and they’ll be able to obtain the man’s last address from the pawnbroker.

Outside the pawnbroker, Watson is approached by a gypsy woman who claims she knows about him and Mary. He tells the woman to tell him his fortune, and she tells him that marriage is a bad idea, as it’ll consist of Mary growing fat, print wallpaper and doilies. Holmes solemnly echoes everything she says, and Watson realizes this was a huge setup on Holmes’s part. He asks if Holmes has no shame, and then – just to spite Holmes – buys an engagement ring for Mary on the spot.

After Watson purchases the ring and Holmes has obtained the red dwarf’s address, Holmes makes to go in and examine the building. Watson tells him he can’t follow, as he has a dinner planned with Mary’s parents. Holmes looks disappointed but understanding, and goes in alone. Watson stands in the street for a minute before sighing to himself, and follows.

Holmes is in the middle of picking the lock on the red dwarf’s door – he has a utility belt that made me think of Batman’s – when Watson just kicks the door in. They greet each other cheerfully, and go into the room.

The room is in shambles, filled with medical equipment and experimented-on animals. Watson finds a piece of paper with Lord Blackwood’s watermark – effectively linking the red-headed dwarf to Blackwood – and Holmes snips the tail off of a experimented-on (and dead) rat.

The duo also notices a plate with some kind of melted substance and honeycombs. Holmes is right in the middle of saying that everything fits in with what he’s been thinking, but there was one smell he couldn’t identify. Just as he’s talking, two men eating caramel apples (the scent that Holmes was smelling) appear in the doorway, and Watson calls Holmes’s attention to them.

Holmes notes that they’re carrying canisters in their hands, and asks the men if they’re here to burn down the building. They smile sinisterly and say yes, and then call out for their colleague – an extremely large man who only speaks French.

A brawl between Watson, Holmes and the three men begin in earnest. Watson takes on the two associates, while Holmes takes on the French man. As they fight, Holmes pauses to catch his breath, and ask for a moment, and the French man shrugs and politely says it’s not a problem.

The fight comes to a head when Holmes discovers an electricity-powered rod amongst the redheaded dwarf’s things. He wields it at the French man, and it zaps him with enough force to throw the man backwards. Even though Holmes admits that he doesn’t know how it works, he chases the French man out of the room with it. Watson is left to finish off the two associates, but not before accidentally dropping Mary’s engagement ring.

Holmes chases the French man down the street and into a London shipyard. There’s a half-finished boat in the yard, and the men all look up in interest as Holmes threatens to zap the man. He asks the man who he works for, and the French man responds, “You know who”, before reaching over and crushing the rod. Now defenseless, Holmes can only run.

A long, long time ago, a drop of sunlight fell from the sky, and when it touched the Earth, a glowing yellow flower blossomed. The flower was found by a woman named Mother Gothel, who soon learned that when she sang a certain song to the flower, it exuded a power that restored her youth.

Centuries passed, and a kingdom grew and prospered nearby. After sometime, the King and his Wife were expecting their first child, but as her due date approached, the Queen fell deathly ill. There was an old rumor that a glowing yellow flower created by a drop of sunlight could cure any illness, and so the soldiers of the kingdom searched far and wide, and finally found the flower that Gothel had been hoarding for many years.

The flower was distilled into an elixir which saved the Queen’s life. She soon gave birth to a little girl who, unlike her parents, had beautiful golden hair. Giving her the name Rapunzel, the Royal family held a celebration, in which they sent aloft a glowing paper lantern.

Mother Gothel, however, had seen the soldiers take the flower and was determined not to lose it’s magical powers. She stole into the castle late one night and, upon finding Rapunzel in her crib, recited the song. The girl’s hair glowed yellow just like the flower, but when Gothel attempted to clip some hair in hopes to use it to restore her beauty, the clipped hair turned brown. So Gothel kidnapped the young girl and fled with her deep into the forrest.

Taking her to a secret tower, Mother Gothel raised the girl to think that she was her mother, teaching her the song and relying on her for youthful restoration. As the years went by, Rapunzel was fascinated by a strange grouping of light that took place on the same day as her birthday. Unknown to her, the releasing of lanterns is a tradition of the King and Queen, in hopes their daughter will return to them one day.

Over the years, Rapunzel grows into a creative young woman, trying to amuse herself in her tower as Mother Gothel comes and goes as she pleases. Rapunzel also befriends a little chameleon named Pascal. Though she claims that she likes staying in her tower, she longs to leave it and see the world, especially the floating lights that occur on her birthday.

A few days before her birthday, Mother Gothel visits her, and Rapunzel gets up the nerve to ask Gothel to take her to see the floating lights. Gothel quells Rapunzel’s interest by scaring her into thinking that the world is too dangerous for someone as naive as her, and that people will want to capture her for her magic golden hair. Sadly, Rapunzel promises to not ask to leave the tower again.

After Mother Gothel leaves, Rapunzel is shocked when a young man makes his way into the tower. After hitting him over the head with a frying pan and hiding him in her closet, Rapunzel now feels that Mother Gothel was wrong, and that if she was able to subdue a person and put him in a closet, maybe she can take care of herself! However, when Mother Goethel returns and tries to broach the subject again (trying to lead up to revealing the young man in her closet), Mother Gothel loudly proclaims that Rapunzel will never leave the tower.

Quickly, Rapunzel changes the subject, and requests that Mother Gothel get her some seashells to make more white paint with. Mother Goethel is not pleased to make a 3-day journey for this, but does so in hopes that this will turn Rapunzel’s mind away from leaving.

After she is gone, Rapunzel releases the young man, and tying him in a chair with her hair, finds that his name is Flynn Rider. Flynn claims he was just looking for a place to hide, having stolen a tiara from the neighboring kingdom. Rapunzel takes his satchel and the tiara contained within, and makes a deal with Flynn: if he will take her to see the floating lanterns and return her to her tower, she will give him back his satchel and the tiara. Reluctantly, Flynn agrees.

After making her way out of the tower, Rapunzel struggles with her emotions: excited to see the world for the first time, but also deeply guilty that she has defied her ‘Mother.’ Flynn offers to return her, but Rapunzel claims she will be alright.

Hoping to get her to change her mind, Flynn takes her to a place called The Snuggly Duckling, which is overrun with a group of ruffians. However, the ruffians recognize Flynn as a wanted man of the neighboring kingdom, and send one of their associates to alert the Palace Guards. However, Rapunzel pleads with the men to let Flynn go, and how she needs him to fulfill a dream she’s had all her life. This melts the hearts of the ruffians, who each reveal dreams of their own.

However, the Palace Guards soon enter, and Rapunzel and Flynn escape through a secret passageway. This leads them to a quarry, where Flynn is soon cornered by the Palace Guards, a Palace horse named Maximus, and two of Flynn’s cohorts from whom he attempted to flee with the tiara.

As Rapunzel and Flynn attempt to escape, Maximus dislodges a piece of wood from a makeshift dam nearby, attempting to use it to walk over a cliff area…only to have the dam break and flood the area. Rapunzel and Flynn make it into a cave, but are soon trapped when rocks cover the entrance, and water from the broken dam begins to fill up the empty space. Feeling that they may soon die, the two then confess a secret to the other: Flynn reveals that his real name is Eugene Fitzherbert, and Rapunzel reveals that her hair glows when she sings. Realizing this can work to their advantage, she quickly sings, and the illumination from her hair allows Flynn to dislodge some of the rocks at the entran ce, and the two escape.

Meanwhile, Mother Gothel has returned from her journey early, and having found Rapunzel gone from the tower, but the satchel and tiara there along with a wanted poster of Flynn, sets out to bring her ‘daughter’ back. Arming herself with a dagger and trailing the two to the Snuggly Duckling, she soon learns that they have escaped through a tunnel, and manages to find where the tunnel ends. When she gets there, she instead finds Flynn’s two cohorts. Hoping to use them to her advantage, she gives them back the satchel and tiara that Flynn had, but claims she knows of something worth much more, and can also help them exact revenge on Flynn Rider.

As night settles, Flynn and Rapunzel camp for the night, and Rapunzel uses her hair to heal a wound on Flynn’s hand from the escape. As they talk, Flynn reveals why he does not go by his given name of Eugene. As an orphan, he was entranced by stories of a thief named Flynn, and the daring to have enough money to go anywhere he wanted intrigued him. Even so, Rapunzel claims that she likes the name Eugene better.

After Flynn goes off to get some more wood for their fire, Mother Gothel appears to Rapunzel, and intends to take her back to the tower. However, Rapunzel refuses to go. When she claims that she thinks Flynn likes her, Gothel reveals the tiara and satchel, claiming that’s all Flynn really cares for. Gothel gives these to Rapunzel and tells her to give them to Flynn to prove her right.

Fearing that Gothel is telling the truth, Rapunzel hides the items when he returns, and they settle in for the night, with Gothel and Flynn’s former cohorts watching from a distance.

The next day, the horse Maximus finally tracks down Flynn, intending to turn him in. However, Rapunzel convinces Maximus that she needs Flynn to show her the lanterns, and the horse gives in to her 24-hour reprieve. The group then makes their way to the nearby kingdom, where Rapunzel has her hair weaved into an extra-large braid to keep it from getting trampled, and views an intricate tile portrait of the Royal family, including a blonde baby girl.

As the day wears on, Rapunzel and Flynn grow closer together until it’s time for the lantern ceremony. The two take a boat out onto the nearby waters, and are in awe as the lanterns cast a romantic setting upon the water. Rapunzel then reveals the satchel and tiara, but unlike what Goethel told her, Flynn does not seem to care about these. As they watch the lanterns , they then confess their feelings for each other, but before they can kiss, Flynn spots his cohorts on the nearby shore.

Bringing the boat to shore, Flynn meets his cohorts, and apologizes for his actions, giving them the satchel and the tiara. However, they now claim they don’t want it.

As she waits by the boat, Rapunzel is shocked when the two cohorts approach her, and point out a boat sailing towards the kingdom, with Flynn at the wheel. The two claim he took the crown and left, leaving them to capture Rapunzel and her magical hair. Rapunzel attempts to flee, but is saved when Mother Gothel appears, knocking out the two men. Rapunzel then returns with her “mother”, promising never to disobey her again.

In reality, the two men knocked out Flynn, and lashed him and the tiara to the wheel of the ship. As it arrives at the kingdom’s port, Flynn is arrested.

Back in her tower, Mother Gothel sends Rapunzel to her room, claiming they’ll forget everything that happened. However, as she looks around her room and at the sun emblem of the kingdom she obtained while she was there, Rapunzel notices that within a number of her drawings, the same symbol occurs, and she suddenly realizes that she is the missing Princess for whom the lanterns are for!

Rapunzel goes to Mother Gothel wanting to know the truth. Realizing that she has been lied to all her life, Rapunzel attempts to leave but not before Gothel stops her from going after Flynn, claiming that he has by now been captured by the Palace Guards who most likely will execute him as soon as possible.

In the kingdom, Flynn is led to the gallows, but stops when he comes across his cohorts, wanting to know what they did to Rapunzel. They claim they were acting under the order of Mother Gothel to get Rapunzel back.

As Flynn is about to be led into the courtyard gallows, The ruffians from the Snuggly Duckling along with Maximus break Flynn out. Maximus then helps Flynn return to the tower.

When Rapunzel’s hair ascends to the ground, Flynn climbs up it, but is shocked when he sees Rapunzel bound and gagged, and is soon stabbed by Gothel with a dagger. Gothel then leaves Flynn to die, trying to drag Rapunzel out another exit, promising to take her somewhere where no one will find her.

As she struggles watching Flynn in pain, Rapunzel promises she will go with Gothel without resistance, if she can use her magic hair to save Flynn.

Gothel agrees, but chains Flynn to keep him from getting away. Flynn begs Rapunzel not to do this, saying that her promise will never allow her to be free. As she attempts to recite the magic incantation, Flynn gets hold of a broken piece of the nearby vanity mirror, cutting off Rapunzel’s long hair, breaking its enchantment.

This then causes Mother Gothel to age quickly, driving her into a state of shock that causes her to fall out the nearby window. Aging several centuries in a matter of seconds, her cloak then hits the forest floor, and all that remains of the vain woman is a a cloud of dust.

As Rapunzel watches, Flynn dies in her arms. Her eyes filled with tears, she finishes reciting the incantation, even though her hair has now turned to a more natural brown color. However, as a tear falls on Flynn’s face, the last magic of the sunflower restores Flynn to health, and the two lovers unite in a kiss.

Flynn and Rapunzel then return to the kingdom, where Rapunzel is reunited with her parents. Flynn is welcomed into the family, and after a celebration to mark the return of the Princess (in which we see that the ruffians have also fulfilled their own dreams), it is revealed that eventually, Flynn (aka Eugene) and Rapunzel were married soon after.